Press brakes are commonly used to bend sheet-like workpieces, such as sheet metal. A conventional press brake has an upper beam and a lower beam, at least one of which is movable toward and away from the other. Typically, the upper beam is movable vertically while the lower beam is fixed in a stationary position. It is common for a male forming punch and a female forming die to be mounted respectively on the upper and lower beams of a press brake.
Typically, the punch has a downwardly-oriented, workpiece-deforming surface (or “tip”). The configuration of this surface is dictated by the shape into which it is desired to bend a workpiece. The die typically has a recess that is aligned with the tip of the punch. The configuration of this recess corresponds to the configuration of the workpiece-deforming surface of the punch. Thus, when the beams are brought together, a workpiece between the two is pressed by the punch into the die to give the workpiece a desired bend.
From time to time, it is necessary to mount and dismount press brake tools. The manner in which a press brake tool is mounted on, and dismounted from, a tool holder depends upon the configuration of the tool. For example, U.S. Pat. No. 5,245,854 (issued to Bruggink et al., and assigned to Mechinefabriek Wila B. V.), the entire teachings of which are incorporated herein by reference, discloses a punch that is adapted for both vertical mounting and vertical dismounting. Here, the punch has a projection P that is biased by a spring toward an extended position in which the projection P extends outwardly through an opening in the side surface of the punch's tang. When the projection P is in its extended position, it P is adapted to engage a safety slot S/S defined by the tool holder. The punch has an actuator (a button) that is connected to the spring-biased projection P such that when the actuator is actuated (when the button is depressed), the projection P is moved (overcoming the bias of the spring) to its retracted position. When the projection P is retracted, the punch can be moved upwardly for mounting or downwardly for dismounting.
In more detail, the punch taught in this Wila patent is mounted by moving it upwardly into the downwardly-open channel of the tool holder (while the projection P is held in its retracted position by depressing the button). Once the punch is moved into its operative position (wherein the tang of the punch is received in the channel of the tool holder), the actuator is disengaged (by releasing the button) and the bias of the spring moves the projection P into its extended position so as to engage the safety slot S/S of the tool holder. Later, when it is desired to dismount the punch, the actuator is again actuated to retract the projection P, causing it P to disengage from the safety slot S/S of the tool holder, whereafter the punch can be removed downwardly out of the channel of the tool holder.
Thus, the punch in this Wila patent can be removed from the tool holder by moving the punch downwardly while the projection P retracted. While vertical dismounting is quite desirable in some cases, it can be a significant disadvantage in certain respects. For example, when the actuator on the punch is actuated (by depressing the button), the full weight of the tool is instantaneously released upon the operator. In some cases, this is less than ideal, such as when heavier (e.g., longer) tools are used.
On heavier tools, Wila provides one or more fixed dowels on each tool. Consequentially, these tools are dismounted by sliding them lengthwise out of the tool holder, rather than by removing them downwardly. This is advantageous in that it avoids the sudden release of the tool's full weight upon the operator. Unfortunately, these tools must also be mounted horizontally due to the fixed dowels. It is desirable to be able to mount press brake tools by moving them upwardly from below the upper table of a tool holder and, unlike dismounting, mounting normally does not involve any sudden release of the tool's weight.
Further, the fixed dowels on these Wila tools are circular in cross section. Unfortunately, these round dowels tend to deform (e.g., gouge) the planar beam surface on which the dowels slide when a punch of this nature is removed from a tool holder. This is because the weight of the punch is effectively concentrated on the one or more single points of contact that exist between the round dowels and the planar beam surface on which the dowels slide. This can cause unnecessary beam damage and therefore is less than ideal.
It would be desirable to provide a press brake tool that can be mounted vertically, and can be dismounted horizontally (i.e., by sliding the tool lengthwise from the tool holder), but cannot be dismounted vertically. It would be particularly desirable to provide a tool of this nature wherein the contact between tool and the beam surface on which the tool slides during removal is broader than just one or more single points of contact (e.g., wherein the tool has one or more safety keys each defining a flat adapted to slide along a surface of the beam during removal), such that beam deformation is less likely when the tool is dismounted.